A Lexical Knowledge Representation Model for Natural Language Understanding

Introduction

A natural language represents and models information of real world entities and relations. There exist a large number of entities in the world, and the number of relations among entities is even higher. Entities and relations together make a highly complex multiple dimensional lattices. It is not a surprise that it usually takes a lot of training for a human being to speak, write and understand a natural language even with the fact that the computation power packed in a small human brain surpasses the most powerful supercomputer in many aspects.

Human beings receive information through vision, hearing, smelling and touching, and send information through facial and body expressions, talking and writing. Of these communication channels, reading (from human vision), hearing, talking and writing are related to natural languages. All of them are temporally one-dimensional, and only one signal is sent out or received at a certain time point, so a natural language is communicated one dimensionally. With one-dimensional natural languages used by human being, in order to understand and describe a highly dimensional environment a series of filtering and transformations are necessary as illustrated in Figure 1. These transformations can be N-dimensional to N-dimensional or one-dimensional to N-dimensional in input process, and N-dimensional to one-dimensional or N-dimensional to N-dimensional in an output process. After these transformations information should be ready to be used by the central processing unit directly. Effectiveness and efficiency of these transformations are very important to knowledge representation and management.

Figure 1.

Communication process for a knowledge-based system

A knowledge model describes structure and other properties of a knowledge base which is part of a central processing system. A knowledge representation model is simply a mirror of our world, since one important requirement for a model is its accuracy. In this sense there is hardly any intelligence in a knowledge model or a knowledge base. Instead it is the communication process consisting of filtering and transformations that shows more intelligent behaviors. As expressed by Robert C. Berwick, et al., in a white paper of MIT Genesis project (Berwick, et. al., 2004), “The intelligence is in the I/O”. As shown in Figure 1, a knowledge model may be the easiest component to start since its input has been filtered and transformed tremendously from the original format, and is ready to be stored in the knowledge base directly. On the other hand, a knowledge representation (KR) model plays a central role to any knowledge-based systems, and it eventually decides how far such a system can go. Furthermore, knowledge and experience can make the process of filtering and transformations more efficient and effective.

A KR model captures the properties of real world entities and their relationships. Enormous amounts of intervened entities constitute a highly complex multi-dimensional structure. Thus a KR method needs powerful expressiveness to model such information.

Many cognitive models of knowledge representation have been proposed in cognitive informatics. Several cognitive models are discussed in (Wang & Wang, 2006). Object-Attribute-Relation model is proposed to represent the formal information and knowledge structures acquired and learned in the brain (Wang, 2007). This model explores several interesting physical and physiological aspects of brain learning and gives a plausible estimation of human memory capability. The cognitive foundations and processes of consciousness and attention are critical to cognitive informatics. How abstract consciousness is generated by physical and physiological organs are discussed in (Wang & Wang 2008). A nested cognitive model to explain the process of reading Chinese characters is presented in (Zheng, et. al., 2008), which indicates that there are two distinctive pathways in reading Chinese characters, and this can be employed to build reading models. Visual semantic algebra (VSA), a new form of denotational mathematics, is presented for abstract visual object and architecture manipulation (Wang, 2008). VSA can serve as a powerful man-machine interactive language for representing and manipulating visual geometrical objects in computational intelligence systems.